Please help with spark plug question on 572's
 

Have a set of 572's I'm doing plugs on. Existing are champion N9YC. They are all showing dark and some slightly wet. Called oreillys and the NGK cross comes to a resister 5 heat range plug??? Seems way too hot for my liking! Motors don't seem to miss a beat when running. No loading up it seems, missing, running hot, or blackened transom....any suggestions other than going to a stupid hot plug? Merlin tall decks, brodix alum heads. Aprox 80 hrs on motors

What's wrong with getting what's in it now? I would run a denso iridium plug with that combo. Also what do u mean by some slightly wet?? As in gas on them... U got a hot ingnition I'm assuming. If it ran 80 hrs with what's in there just fine then I would just use them. Plugs are not such a big deal to go up or down in the heat range UNLESS u have nitrous or a blower. Then u can cause prob when jumping around!!

Ngk 5's should be fine unless u have alot of compression or the timing way off. Plugs should look like milk chocolate.

Just seems a 5 plug would be much too hot for the constant load. I can see throwing one in a push mower but not anything performance marine....most searches on here net 9's, 8's, and a very few 7's.....much less 6's or in my case 5's. Yes some are slightly glossy....most dry black and 1 black with a slight tint of observable brown. Average plug is just solid black. Thread heat discoloration is 4 threads down. Any of you know anyone running this hot of plug in marine performance use? I wonder if these plugs were thrown in to make up for a richer mix with a lower base advance? Maybe I'm over thinking....just like to know it's close to right before heading back out for my second run. I only have had it out once thus far.

The Champion plug you pulled out crosses to a 6. I'm pretty sure a 6 comes in alot of the merc engines including hp's I usually run 6's in naturally aspirated motors. I've run 6's on 11:1 pump gas steel headed marine motors 32 degrees timing run hard for long periods of time and never had an issue. What size carb is on this thing?

They have 1050 doms. They are resister plugs so I believe they cross to the br5. I am looking up information on the rapid fire #5's as we speak (3/4" thread with washer for flat contact surface). Any word on these rapid fires? Looks like they cross to 6 ngk's. I appreciate the help